The present invention relates to a technique for preventing a radar device from erroneously determining different pieces of object information as a single object.
In general, a radar device which is mounted in a vehicle continuously scans the periphery of the vehicle, when the same object has been detected multiple times, outputs object information (for example, the relative distance between the vehicle and the object, the relative speed, the lateral distance (angle), and the like) to a vehicle control section in accordance with the positional relationship between the object which has been detected multiple times and the host vehicle, and performs vehicle control (warning, brake, seat belt tightening, or the like).
In performing continuous scanning, with regard to a newly detected object, when the object is continuously detected a predetermined number of times or more, object information is output to the vehicle control section. That is, when the object is detected once only in scanning, object information is not output to the vehicle control section. When the object is detected multiple times, processing is performed in which changes in the positional relationship between the object and the host vehicle are calculated, and if the conditions for the output to the vehicle control section are satisfied, the object information of the target object is output to the vehicle control section.
The detection of an object is done on the basis of a signal which is received as a received wave by the radar device when a transmission wave from the radar device is reflected from the object. The radar device may receive a plurality of reflected waves from a single object. In this case, a signal processing section of the radar device sets a reflection point at the closest relative distance from the host vehicle as a representative detection point, and determines all of detection points within a predetermined distance range (coupling range) from the representative detection point as a single object. The object information is output from the radar device to the vehicle control section.
When a representative detection point which has been detected once is not detected in subsequent scanning, if there is a detection point second-closest to the host vehicle next to the representative detection point which has not been detected in current scanning, from among the detection points within the coupling range previously detected, the detection point is set as a new representative detection point, the coupling range is again set on the basis of the new representative detection point, and processing is performed assuming that the same object is continuously detected after previous scanning. JP-A-2006-38755 describes a technique related to the present invention.
However, when a coupling range is provided and a plurality of detection points are determined to be a single object, even though detection points of different objects fall within a single coupling range, it may be determined to be the detection points of a single object. For example, when a vehicle is traveling by closely following another vehicle, all reflection points of different vehicles may be determined as a single object.
For this reason, when a representative detection point which has been detected in past scanning is not detected in subsequent scanning, or when a detection point second-closest to the host vehicle next to the representative detection point which has not been detected, from among the detection points within the coupling range in past scanning is a detection point of another vehicle different from the vehicle which has previously been detected, the detection point of another vehicle may be erroneously set as a new representative detection point of the same vehicle which has previously been detected. In this case, the set representative detection point is intrinsically a detection point of a vehicle which is newly detected. In the vehicle control section to which object information is output, if an object is not detected as the same object multiple times, the object is not subjected to vehicle control, thus the object information of the representative detection point will not be subjected to vehicle control intrinsically. For this reason, the radar device erroneously recognizes different objects as a single object, such that the vehicle control section performs vehicle control on the basis of object information which is not intrinsically subjected to vehicle control, causing erroneous vehicle control.